Lower Salmon DamGets a Makeover

by Tetona Dunlap
Twin Times-News, December 3, 2015

HAGERMAN -- Crews had to work quickly as a giant blue rotor emerged slowly from inside the Lower Salmon Falls Dam. Weighing 120 tons, the piece moved about a foot a minute, powered by an overhead crane.

Installation of the rotor was postponed twice because of rain and wind. And with the cold and breezy weather last week, crews worked diligently to maneuver it in place before the gray clouds produced moisture.

"Because it's an electrical piece of equipment, we want to keep the rain out," said Mike Burkholder, Idaho Power engineer and project manager. "Even today we are pushing it."

A massive $8 million maintenance project is underway to refurbish one of four turbines at the Lower Salmon Falls Hydroelectric Project, where specialists from Idaho Power's Hagerman shop have been working for months. The plant has a generating capacity of 60 megawatts -- enough energy to power about 41,000 homes. It also includes a dam and powerhouse with four generators.

The project started in February and is expected to wrap up by the end of this year. It is one of several maintenance projects Idaho Power has planned for the next couple of years.

"This level of work is really something we'd normally see every 10 years or so," said Brad Bowlin, an Idaho Power spokesman. "We do concrete repair work on the dams almost every year. Maintenance is a regular part of operating the system."

The Upper Salmon Falls, Lower Salmon Falls and Bliss projects are among the 17 hydropower projects that Idaho Power owns and operates on the Snake River and its tributaries. The three projects are known collectively as the Mid-Snake Projects. The Mid-Snake Projects operate under licenses issued by the Federal Energy Regulatory Commission, or FERC.

The project is part of Idaho Power's ongoing maintenance of its hydro fleet, which provides about half of the electricity the company's customers use each year, Bowlin said.

The dam on the Snake River near Hagerman was built in 1910 by the Greater Shoshone and Twin Falls Water Power Company. Idaho Power acquired the plant in 1916 and rebuilt it in 1949. This is the first time any of the turbines have been refurbished since. A new runner was installed, while other parts of the turbine -- such as the rotor -- were refurbished.

"Turbine refurbishments like the one at Salmon Falls are scheduled every year or two," Bowlin said. "Many of the units are 50 to 80 years old and are due for repairs. If we can gain additional efficiency by putting in new runners while we are doing the rest of the work, then we go ahead and do that if it makes economic sense."

Putting in a new runner can increase efficiency by 3 to 5 percent on some units, Bowlin added.

Besides the weather, maneuvering the nearly 20-foot wide rotor to fit perfectly was another obstacle. The shaft was bigger than the rotor. This meant the rotor had to be heated while the shaft was cooled. For them to fit together, there had to be a 50 degree difference between the two. When put in place there would 3/8 of an inch on either side of the rotor.

Since the turbine has been refurbished, the other three units have remained online. The fourth turbine was refurbished because it was in the worst condition due to cavitation -- erosion due to water -- and normal wear, Burkholder said.

Other upcoming maintenance projects include the replacement of four small turbines at Brownlee Dam, Idaho Power's largest hydro facility. Replacement of those four units and a large turbine will cost about $40 million over five years.

"A turbine replacement is scheduled to begin at the Upper Malad project within the next several weeks and it will be completed next year," Bowlin said. "We recently rebuilt a bridge over the Malad River that our crews use to access the Malad project."

The Malad Project consists of two dams within a two-mile reach of the river near Hagerman. Its first full year of operation was in 1949. Estimated cost is about $4 million.

At the Twin Falls power plant, crews are finishing some maintenance and upgrade work.

"We replaced wooden flash boards at the top of the dam with concrete. This will reduce maintenance and the need to regularly draw down the reservoir during that maintenance, so it is a benefit to users as well as a safety improvement for our workers," Bowlin said. "As part of that project, a new boat dock is being installed. It could be done as early as this week. The overall project is scheduled to wrap up before the end of March."

The first phase of a major set of upgrades at Shoshone Falls finished in early November, Bowlin said. This included upgrades to the spillway, the intake structure and scenic flow channel.

"We plan some major work at the Shoshone Falls power plant itself in the next couple of years," he said, "but the details of that are still being finalized."